Field of the Invention
The present invention associates with non-contact power supply devices which perform electric power transmission and reception by means of their coils by utilizing a magnetic field coupling therebetween, and relates to a bidirectional non-contact power supply device functioning as an electric power transmission device and an electric power reception device, and to a bidirectional non-contact power supply system.
Description of the Related Art
A contactless or non-contact power supply device which supplies electric power from one coil to the other coil by utilizing coupling of a magnetic field therebetween generated by the one coil is considered as charging means to electric automotive vehicles, a household electric apparatus and the like. ln recent years, by connecting coils in series or parallel with capacitors, an electric power supply is increasingly performed with high efficiency even when the distance between the coils through which electric power is transmitted and received is large in separation.
Attempts are being made where such a non-contact power supply is utilized not only for an electric power supply in one direction for charging an apparatus, but also for discharging from an apparatus having been charged to another apparatus.
For example in a conventional bidirectional non-contact power supply device which utilizes coupling of a magnetic field with another coil, capacitors are provided in series and parallel with a coil for performing electric power transmission and reception; and a switch is provided in parallel with the series-connected capacitor, and another switch, in series with the parallel-connected capacitor. According to this arrangement, it is so configured that, by selecting turn-on and turn-off of the switches, either one of a configuration in which a capacitor is connected only in series with the coil and a configuration in which another capacitor is connected only in parallel with the coil can be selected. And then, a thing in which the coil and the capacitors are connected in series and parallel therewith is connected to a full-bridge inverter circuit. The full-bridge inverter circuit operates as an inverter when electric power is supplied from the inverter circuit to a side of the coil, and operates as a diode bridge when electric power is supplied from the side of the coil to the inverter circuit. And then, another end of the full-bridge inverter circuit is connected to a bidirectional buck-boost converter, and its other end of the bidirectional buck-boost converter is connected to a DC power source. The bidirectional buck-boost converter is configured to operate as a step-up or boost chopper circuit when electric power is supplied from the DC power source to a side of the full-bridge inverter circuit, and, as a step-down or buck chopper circuit when electric power is supplied from the side of the full-bridge inverter circuit to the DC power source. In a conventional bidirectional non-contact power supply system, bidirectional non-contact power supply devices in the configurations described above are configured to form a pair.
And then, when a non-contact power supply is performed, one bidirectional non-contact power supply device operates as an electric power transmission device, and the other bidirectional non-contact power supply device, as an electric power reception device. When the operation as an electric power transmission device is ensued, a configuration is transferred in which a coil and a capacitor is connected in series with each other by changing over switches for selecting capacitors which are connected in series and parallel with the coil. And then, the bidirectional buck-boost converter inputs a voltage of the DC power source into the full-bridge inverter circuit, while maintaining the voltage as it is, or after having performed voltage regulation on an as-needed basis. A DC voltage from the DC power source is converted by means of the full-bridge inverter circuit into an alternating current, which is supplied to a coil and a capacitor connected in series with each other. Meanwhile, when the operation as an electric power reception device is ensued, a configuration is transferred in which a coil and another capacitor is connected in parallel with each other by changing over switches for selecting capacitors which are connected in series and parallel with the coil. Electric power received by a coil and a capacitor connected in parallel with each other is AC power, and is supplied into the full-bridge inverter circuit; however, because the full-bridge inverter circuit operates as a diode bridge, the AC power having been received is converted into DC power, and is supplied to the bidirectional buck-boost converter. The bidirectional buck-boost converter steps down the electric power having been received to a DC voltage of an appropriate magnitude. and supplies it to a load. In a case of charging electric power, the load can be made as a DC power source which is a secondary battery (for example, refer to Japanese Laid-Open Patent Publication No. 2012-244635).